The present invention relates to a map display apparatus for a motor vehicle, which is capable of displaying a road map around a vehicle position on a display device.
There is known a map display apparatus for a motor vehicle, which displays a road map in the form of a socalled bird""s-eye view, namely, displays the road map on a display device such that the road map around the current position of the vehicle (vehicle position) is displayed in a larger scale than a far side view (refer to laid-open Publication No. 2-244188 of unexamined Japanese Patent Application, for example). The apparatus disclosed in the above-identified publication places a view point behind the current position of the vehicle, and displays a view taken by looking down the map from this view point in the travelling direction of the vehicle, on a screen of the display device. In this manner of displaying the bird""s-eye view, it is possible to display map information around the current position in a larger scale, and also display a wide range of map information ranging from the current position to a distant place. This makes it easier to visually grasp conditions of junctions of roads. Further, the road map can be displayed with an increased sense of reality as if the driver himself/herself actually looked down the road map.
In the case where the original map information has a little to be displayed on the screen, as in the case of displaying a road map of a suburban area having a low density of roads, however, it is difficult to determine whether a bird""s-eye view or a conventional planimetric map is being displayed, and the sense of reality as an intrinsic feature of the bird""s-eye view cannot be achieved even when the bird""s-eye view is displayed. Further, upon display of the road map in the bird""s-eye view, the map scale is continuously varied from the lower edge of the screen toward the upper edge, making it difficult to grasp a sense of distance.
In addition, it is true of both of the bird""s-eye view and the planimetric map that the size of the display screen limits a range of the road map that can be displayed on one screen. When the destination is located a remote distance away from the current position, therefore, the current position and the destination may not be displayed at the same time. If the destination is not displayed, the driver is likely to make an error in the travelling direction.
The object of the present invention is to provide a map display apparatus for a motor vehicle, which is capable of displaying a bird""s-eye view that makes it easier to grasp a sense of distance and recognize the direction of the destination.
To accomplish the above object, the present invention is applied to a map display apparatus for a motor vehicle comprising: road map storage device which stores road map data relating to a road map; a display device capable of displaying the road map; bird""s-eye view data converting circuit which converts the road map data into bird""s-eye view data so that a bird""s-eye view taken by obliquely looking down the road map from above is displayed on the display device; and display control circuit which displays a plurality of grid lines such that the grid lines are superposed on the bird""s-eye view. Since the plurality of grid lines are displayed at the same time that the bird""s-eye view is displayed, the driver can easily grasp a sense of distance, and the bird""s-eye view can be displayed as if it were actually present in the world.
If a display screen of the display device is divided into regions in the vertical direction, and an image representative of the sky, instead of the road map, is displayed in at least one of the divided regions which is closest to the upper edge of the display screen, the bird""s-eye view can be displayed with higher degrees of reality and stability.
The present invention is also applied to a map display apparatus for a motor vehicle comprising: road map storage device which stores road map data relating to a road map; a display device capable of displaying the road map; vehicle position detecting device which detects a current vehicle position; a destination setting circuit which sets a destination of the vehicle; bird""s-eye view data converting circuit which converts the road map data into bird""s-eye view data, so that a bird""s-eye view taken by obliquely looking down the road map from above is displayed on the display device; determining circuit which determines whether data relating to the destination is included in the converted bird""s-eye view data or not; and display control circuit which displays a mark at a display position corresponding to the destination if an affirmative decision is obtained by the determining circuit, and displaying the mark at a certain position in a display screen of the display device, which position lies in a direction of the destination, if a negative decision is obtained by the determining circuit.
Since the mark indicating the direction of the destination is always displayed irrespective of the distance to the destination, the driver can drive while constantly being aware of the direction of the destination, and is thus prevented from getting lost.